..Heritability for individual differences in the intercept was estimated at 77%. For the item 'Nobody loves me' no significant trend over age was seen; the heritability of the intercept was estimated at 70%...

..Non-shared environmental effects accounted for the remaining covariance over time...

The genetic and environmental structure of verbal and visuospatial memory in young adults and children

Marieke van LeeuwenDepartment of Biological Psychology, VU University Amsterdam, and Division of Psychosocial Research and Epidemiology, The Netherlands Cancer Institute, Amsterdam, The NetherlandsNeuropsychology 23:792-802. 2009

..At the environmental level, in both age cohorts, environmental factors create differences between these domains...

An fMRI study in monozygotic twins discordant for obsessive-compulsive symptoms

..To study familial and nonfamilial environmental influences on attention problems and attention-deficit/hyperactivity disorder (ADHD) in monozygotic twins discordant and concordant-high and low for these traits...

The association between low birth weight and high levels of cholesterol is not due to an increased cholesterol synthesis or absorption: analysis in twins

..These results indicate that autistic traits have specific characteristics that are substantially genetically independent from other common but related behavioral domains such as social problems and withdrawn behavior...

A Functional polymorphism under positive evolutionary selection in ADRB2 is associated with human intelligence with opposite effects in the young and the elderly

..The variance in coffee preference (defined as the proportion of coffee consumption relative to the consumption of coffee and tea in total) was explained by genetic factors (62%) and unique environmental factors (38%)...

..To explore genetic and environmental influences on individual differences in autistic traits in early adulthood and to test if there is assortative mating (nonrandom partner choice) for autistic traits in the general population...

..Mutations in one of these genes (growth differentiation factor 9) are significantly more frequent in mothers of DZ twins. However, the mutations are rare and only account for a small part of the genetic contribution for twinning...

Suggestive linkage on chromosome 2, 8, and 17 for lifetime major depression

..A twin design was used to test whether the association between exercise behavior and heart rate and the association between exercise behavior and respiratory sinus arrhythmia (RSA) derive from a common genetic factor...

Environmental factors determine where the Dutch live: results from the Netherlands twin register

..2 for hyperactivity was also found. Heritability of inattention, hyperactivity and total ADHD symptoms is lower in adults than in children. Chromosomes 18q and 2p are likely to harbor genes that influence several aspects of adult ADHD...

Heritability of anxious-depressive and withdrawn behavior: age-related changes during adolescence

..To explain the differential course of anxiety and depression in individuals from childhood to adulthood by examining age-related changes in the genetic and environmental etiology of anxious and depressive symptoms...

Short- and long-term effects of child care on problem behaviors in a Dutch sample of twins

..12 and .23). Children with a larger amount of child care did not show more behavior problems, therefore it was questioned whether the increased levels of behavior problems could be attributed to quantity of child care...

Heritability of selective attention and working memory in preschoolers

..The results showed clear familial resemblances on performance. It proved difficult to ascribe these effects to shared genes or to shared environment. An exception was memory search rate, which was clearly heritable...

..A twin design was used to assess the relative contribution of genetic and environmental influences on the variation in sports participation of Dutch male and female twins between the ages of 13 and 20 yr...

Effects of censoring on parameter estimates and power in genetic modeling

..33-.46) and good for systolic time intervals (.55-.81). When test-retest comparison was limited to two comparable days (two work days or two leisure days), correlations for both SV (.42-.46) and CO (.43-.50) improved...

..To review the methodology of behavior genetics studies addressing research questions that go beyond simple heritability estimation and illustrate these using representative research on childhood and adolescent anxiety and depression...

Genetic etiology of stability of attention problems in young adulthood

..Genetic correlations across time were high, suggesting that the genes that influence variability in attention problems in late adolescence are largely the same as those that influence variability in early adulthood...

Replicated linkage for eye color on 15q using comparative ratings of sibling pairs

..Heritability was 63% for Attention problems, around 45% for Withdrawn, Social Problems, Aggressive Behavior and Rule Breaking Behavior, and around 30% for Anxious/Depressed, Thought Problems and Somatic Complaints...

Variance components models for physical activity with age as modifier: a comparative twin study in seven countries

..To examine whether ceiling effects at long inter beat intervals (IBIs)cause an underestimation of cardiac vagal control in regular exercisers by time and frequency-domain measures of respiratory sinus arrhythmia (RSA)...

The relative contribution of genes and environment to alcohol use in early adolescents: are similar factors related to initiation of alcohol use and frequency of drinking?

..The covariation among the WAIS group factors and the covariation between the group factors and the Raven is predominantly influenced by a second-order genetic factor and strongly support the notion of a biological basis of g...

..The objective of the study was to assess relative maternal and paternal genetic influences on birth timing...

The genetic architecture of neuroticism in 3301 Dutch adolescent twins as a function of age and sex: a study from the Dutch twin register

David C RettewDepartment of Psychiatry, University of Vermont College of Medicine, Bington, Vermont 05405, USATwin Res Hum Genet 9:24-9. 2006

..The magnitude of the genetic component appears higher in the present sample of adolescents than in most studies of adults. The present study suggests that, in adolescence, different genes are expressed in boys and girls...

..These studies typically used DSM ADHD symptoms collected by telephone or interviews with mothers. The purpose of this study was to test the genetic architecture of ADHD by using the ADHD index from Conners' Rating Scales-Revised...

The genetic and environmental contributions to oppositional defiant behavior: a multi-informant twin study

..Although sample specific effects are present, we have shown that genes play a major role in determining the variance of apolipoprotein and lipid levels in four independent twin samples from three different countries...

Meta-analysis of four new genome scans for lipid parameters and analysis of positional candidates in positive linkage regions

Empirical evaluation of the genetic similarity of samples from twin registries in Australia and the Netherlands using 359 STRP markers

Patrick F SullivanDepartment of Genetics, University of North Carolina, Chapel Hill, North Carolina 27599 7264, United States of AmericaTwin Res Hum Genet 9:600-2. 2006

..30% between the Australian and the Netherlands cohorts, a smaller value than between many European groups. We conclude that it is reasonable to combine the Australian and the Netherlands samples for joint genetic analyses...

..There was no evidence of non-random mating for extraversion in the parental generation. Results show that in addition to additive genetic influences, extraversion in adolescents is influenced by non-additive genetic factors...

..Environmental factors affecting height and BMI during growth period are also important, and further studies are needed to identify these factors and test whether they interact with genetic factors...

Dizygotic twinning is not associated with methylenetetrahydrofolate reductase haplotypes

..The aim of this study was to examine whether the drinking habits of parents, siblings, and friends were related to regular drinking in adolescents and young adults, cross-sectionally as well as longitudinally...

Relative risks of adolescent and young adult alcohol use: the role of drinking fathers, mothers, siblings, and friends

..Age differences indicated that these risks decreased with age. Irrespective of age, regular drinking of fathers and mothers posed the lowest risk. Findings were generally the same for males and females...